The present disclosure relates to a multi-device platform. In particular, the present disclosure relates, by way of non-limiting example, to a multi-device platform formed of a plurality of flash storage devices and magnetic storage devices.
Magnetic storage devices such as Hard Disk Drives (HDDs) are capable of providing a large storage capacity with low cost. However, because the HDD uses a read/write head attached to a mechanical arm to read or write data, the performance of the HDD is limited in terms of latency and access performance. Especially when the accessed file is fragmented and written across multiple sections of the magnetic disks or in the case of multiple initiators accessing the same device. Furthermore, in a HDD using shingle-written magnetic recording (SMR) technique, response time is dependent on internal operations such as garbage collection (GC). The amount of GC may vary significantly according to the availability of indirection memory. For example, when the indirection memory is almost full, the HDD requires GC. In particular, the HDD may need to perform defragmentation to reorder the writes to free up indirection memory. The latency variation caused by the decrease of indirection memory can significantly impact the performance of the service, and thereby impact the user experience.
Flash storage devices such as Solid States Drives (SSDs) are capable of providing low latency access performance. Because the memory cells of the SSD can be accessed simultaneously, the speed at which the SSDs read or write data can be much higher than the HDDs, even if the accessed file is fragmented and written sporadically across multiple cells. However, the SSD is considerably more expensive than the HDD in terms of cost per storage capacity.
Together with an increasing diversification of applications and services provided, modern Cloud data centers usually receive mixed multi initiator workloads. In many cases, these workloads change over time. This drives the need for a scaleable and more flexible storage solution which can take advantage of the lower cost of HDDs and the lower access performance of SSDs. Key value attributes are scalability and predictability.